1. Field of the Invention
The present invention relates to database management systems and their use with transportation information systems and spatial geographic information, and more particularly to a spatially integrated relational database using dynamic segmentation for associating linear and spatial information and a method for using the database system with spatial data methods.
2. Description of the Related Art
Commercial relational database management systems have recently provided the ability to store spatial data, but do not support full dynamic segmentation. Commercial graphical information systems (GIS) have provided the ability to store both spatial and relational data, but only in proprietary formats. An anchor section is an underlying spatial referencing mechanism for linear data. In terms of a road network, an anchor section represents a physical section of a roadway, typically a section that connects two intersections.
Commercial GISs do not maintain permanent anchor sections. Currently, GISs break existing anchor sections when a new intersection is identified along an existing anchor section. This proliferates the number of anchor sections, and consequently the size of the database, and also reduces database performance due to this segmentation of anchor sections.
GIS applications have traditionally used a link-node network to represent road networks, where a link represents a section of road. A node, which occurs at the ends of the link, represents either an intersection between links or the end of a road. Because nodes (i.e., intersections) can only occur at the ends of a link, most changes to a road network require splitting of existing links. For example, adding a new intersection in the middle of an existing link requires that the link be split at the intersection point to form two links. Splitting a link has serious adverse consequences. Any references to the original link (e.g., the assignment of a pavement type to a portion of the link) become invalid. In the case of a single data repository, complex data maintenance activities can automatically correct for these changes. However, in a distributed data environment, an automated correction methodology is not feasible.
Many GIS applications use proprietary implementations of dynamic segmentation to associate data values with locations in a roadway. A disadvantage of using such proprietary solutions is that the data within the GIS application is inaccessible to other applications, limiting access to the data by non-GIS users, and making the data more difficult to integrate with other non-GIS data.
Many applications provide access to historical data through periodic snapshots that are stored off-line, thus limiting access to historical data and making it more difficult to perform analyses that integrate historical and current data.
In 1994, the Georgia Department of Transportation (GDOT) initiated a strategic planning process that identified improvements necessary to achieve a greatly improved transportation program. As a result of this strategic planning effort GDOT worked with Georgia Institute of Technology (GTECH) to prepare “A Strategic Plan for Developing a Comprehensive GDOT Transportation Information System (TIS)”, also called the “Plan”, and herein incorporated by reference in its entirety. The Plan examined technologies and processes used for information protocols, data collection, data formats and standards, and communications in the department. The Plan recommended implementation of a transportation information system (TIS) to upgrade data integration, utility and quality of information applications and resources.
GDOT's intention is to share the products of information technology (IT) efforts with other state agencies and the private sector. The state of Georgia is actively developing statewide IT programs that will result in better service delivery and more efficient government. Georgia's IT programs will employ GIS maps developed by GDOT. The maps are also available to the private sector. Two initial systems to be developed were the Transportation Systems and Facilities (TSAF) system and the Transportation Projects subsystem (TPro), the functional specifications of which are in the aforementioned Plan. These two (2) systems combine to create a TIS core module (CM). It is within this context that that an embodiment of the present invention is described.
The Transportation Systems and Facilities (TSAF) system, part of the Transportation Information System (TIS) for the Georgia Department of Transportation (GDOT), is a system designed to provide enterprise-wide access to a large collection of both spatial and tabular GDOT data. TSAF is designed as a relational database and implemented in an Oracle® database which houses the TSAF data, maintenance routines for maintaining this data, and data service routines that provide access to this data over the GDOT intranet through a Web browser. While this configuration is typical for enterprise-wide database systems, TSAF must meet a number of other requirements that differentiate TSAF from most other enterprise-wide database systems.
The GDOT TIS is designed to be a single repository for road network data. TIS will include data for the TSAF and for TPro. The capability to store and retrieve both relational and spatial data must include both GDOT roadways and multi-modal assets. A multi-modal asset is a facility that is related to both a road network and another transportation system (e.g., a park and ride facility). In the example, a park and ride location is related to riding on the road, but does not relate to the road itself. Typically, an multi-modal asset is a transition point between two different transportation systems. A major consideration for the data relating assets with linear attributes such as roadways, railways and transit systems is having a flexible and robust linear referencing system (LRS). Currently GDOT employs more than one linear referencing method (LRM), and in the future may use global positioning system (GPS) coordinates as a location referencing method.
While recognized as desirable, no one to date has implemented an open system for storing and retrieving relational and spatial data in a single repository of road network data. The systems available today do not relate linear, spatial and temporal data in an open system available to third party applications.